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Jean-Daniel Cryans commented on HBASE-2023:
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Ok so in the same order:
- This is the current situation, synchronization at line 613 of HCM.
- Narrowing down the sync block we could put it at line 637 and cover the rest of the locateRegionInMeta
method.
- Removing the sync means getting rid of synchronized at line 613.
> Client sync block can cause 1 thread of a multi-threaded client to block all others
> -----------------------------------------------------------------------------------
>
> Key: HBASE-2023
> URL: https://issues.apache.org/jira/browse/HBASE-2023
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.20.2
> Reporter: ryan rawson
>
> Take a highly multithreaded client, processing a few thousand requests a second. If
a table goes offline, one thread will get stuck in "locateRegionInMeta" which is located inside
the following sync block:
> synchronized(userRegionLock){
> return locateRegionInMeta(META_TABLE_NAME, tableName, row, useCache);
> }
> So when other threads need to find a region (EVEN IF ITS CACHED!!!) it will encounter
this sync and wait.
> This can become an issue on a busy thrift server (where I first noticed the problem),
one region offline can prevent access to all other regions!
> Potential solution: narrow this lock, or perhaps just get rid of it completely.
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